Measuring Diffusion in the Presence of Material Strain

Area of Science:

• Biophysics
• Medical Imaging
• Materials Science

Background:

• Diffusion Magnetic Resonance Imaging (dMRI) measures water diffusion to infer tissue microstructure.
• Material deformation during dMRI acquisition can distort diffusion measurements.
• Accurate microstructural analysis, especially in dynamic tissues like the heart, requires accounting for strain effects.

Purpose of the Study:

• To investigate the impact of material strain on diffusion MRI signal loss.
• To develop and validate a method for correcting strain-induced artifacts in diffusion tensor measurements.
• To highlight the importance of this correction for in vivo cardiac imaging.

Main Methods:

• Theoretical formulation of diffusion signal changes under material deformation using the stretch tensor (U).
• Experimental validation using a gelatin phantom subjected to controlled compression during pulsed-gradient diffusion encoding.
• Development of an MRI-based strain mapping technique for correction.

Main Results:

• Material strain demonstrably alters observed diffusion signal attenuation.
• Compression during diffusion encoding mimics increased gradient strength, affecting diffusion tensor (D) measurements.
• The proposed MRI strain mapping method effectively corrects for these strain-induced perturbations.

Conclusions:

• Material strain is a significant confounder in diffusion MRI measurements.
• An MRI-based strain correction method is presented and validated.
• Accurate assessment of myocardial microstructure in the beating heart necessitates accounting for cardiac deformation during dMRI.